Cardiac PET images suffer from partial volume (PV) losses, a result of motion and limited resolution. A correction can be made using an extravascular (EV) density image, constructed via the subtraction of a blood volume (BV) image from a transmission image (TX, image of tissue density). The ability of the EV image to correct for PV losses is dependent on the noise in the TX image, and by errors in alignment between the TX and BV images. A TX image can be obtained in either a pre-injection or post-injection mode, depending on whether it is taken before or after injection of activity to the subject. The purpose of this study was to determine which TX image best minimizes errors in the EV image. A simple plastic cardiac phantom was used to compare the two TX modes. Calculation and comparison of the centers was used to determine the pre-injection misalignment. Pre-injection offset was -0.33±0.85 mm vertically, and -0.64±0.72 mm horizontally from the post-injection image. A CoV of 0.0231 ±0.004 and 0.0374±0.006 was measured for the pre and post-injection images respectively. These results indicate that the pre-injection TX has the best statistical quality, but provides poor alignment.

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Keywords Extravascular density, Partial volume, Post-injection transmission images, Pre-injection transmission images, Transmission imaging
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Conference SPIE Regional Meeting on Optoelectronics, Photonics, and Imaging, Opto-Canada 2002
Wassenaar, R.W, & De Kemp, R.A. (Robert A.). (2002). Characterization of transmission images for use in resolution recovery of cardiac PET imaging. In Proceedings of SPIE - The International Society for Optical Engineering (pp. 383–385). doi:10.1117/12.2283934